In this paper, we propose to replace frequency domain blind signal separation (FD-BSS) in hands-free speech applications by frequency domain blind signal extraction (FD-BSE). Unlike conventional FD-BSS methods that aim at separating all the signals, FD-BSE extracts only one signal from the mixture resulting in a faster algorithm. After presenting the FD-BSE method based on mutual information minimization, we show that the proposed method enables fast estimation of the background diffuse noise in a hands-free human/machine communication scenario.